Plastic Biodegradation and the Valorization of their Bioproducts: From Trash to Wealth

Plastics are often disposed of in landfills and may require 20 to 1000 years to reach complete degradation. In nature, plastics are slowly degraded through exposure to photodegradation, hydrolytic degradation, thermal degradation, and microbial biodegradation. Of the various approaches, microbial biodegradation is beneficial as the breakdown of plastic polymers can result in the production of simpler monomers. The typical by-products produced include carbon dioxide (CO2), water (H2O), and methane (CH4), among others. In recent years, research efforts have shown that microbial biodegradation can lead to the conversion of plastics into valuable biomaterials. Notably, the hydrolysis of polyethylene terephthalate (PET) by the bacterial strain, Ideonella sakaiensis, resulted in the production of PET intermediates that can be further produced into beneficial polyhydroxyalkanoate (PHA), a biodegradable polymer valued for the development of bioplastics. Bioconversion of plastic wastes are therefore beneficial to the waste management sector. However, the potential of microbes in valorising the by-products of plastic biodegradation is not well explored. Thus, this chapter presents a brief overview of microbial plastic degradation, isolates involved, plastic types, by-products valorised, and the application of these by-products. This would capture the waste to wealth concept of valorisation of plastic waste degradation into useful bioconverted products.